An unsaturated polyester resin composition containing an unsaturated polyester resin, an inorganic filling material, and a fibrous reinforcing material (bulk molding compound: BMC) is widely used in various applications such as the chassis of OA and office equipment, and lamp reflectors typified by headlamps because of its excellent characteristics (e.g., mechanical strength, rigidity, surface smoothness, dimensional accuracy, heat resistance, and moldability).
Although a related-art unsaturated polyester resin composition can be cured and molded to provide a molded article excellent in mechanical strength, rigidity, surface smoothness, dimensional accuracy, and heat resistance, the related-art unsaturated polyester resin composition has a problem in that high content of the inorganic filling material and the fibrous reinforcing material is required in order to maintain these excellent characteristics, resulting in an increase in specific gravity of the molded article. In addition, the unsaturated polyester resin generally provides a molded article having a high specific gravity as compared to thermoplastic resins, and hence its range of utilization has been limited heretofore.
Thus, to solve the problem, various methods of reducing specific gravity have been developed. As a typical method, there is known a method involving reducing the contents of the inorganic filling material and the fibrous reinforcing material, and adding a hollow filler such as glass balloons or silica balloons (see, for example, Patent Literatures 1 and 2).
However, a lamp is constituted by various parts, and a lamp reflector, one of the parts, is fastened to other parts (such as parts for fixing the lamp reflector, fixing a bulb, and a hood for adjusting light) through the use of self-tapping screws. In particular, the lamp reflector is an important part for directing light from a light source in a certain direction. The lamp reflector needs to be fixed at a certain position in order to suppress deviations in light direction.